Piston for internal-combustion engines



Mgy 10, 1927.

0. E. w|| |s YI'STON FOR INTERNAL COMBUSTIONENGINES Filed May 21 192s INVENTOR.

A TTORNEY.

Patented May 10, 1927.

"UNITED STATES:

DURWARD EARLE WILLIS, OF SPRINGFIELD, ILLINOIS.

PISTON FOR INTERNAL-COMBUSTION ENGINES.

Application filed May 21,

This invention relates to improvements in pistons of internal combustion engines.

One of the objects of the invention is the provision of a piston of novel construction made up of dissimilar metals,vi. e. a pistonhead of a metal of a low heat conductivity, and a body and skirt of a metal of, high heat conductivity to the end that heat will be slowly absorbed by the piston but that such. as is absorbed shall be rapidly carried away.

An object is to produce a piston that will conform, in shape to the walls of its cylinder under all conditions to aid in preventing compressed gases in the combustion cham ber reaching the crank-case; that will transmit and dispel heat received at the head thereof; that will as far as possible prevent slapping; and that will have long life.

Another object is that of providing the skirt of a piston with certain peculiarly disposed slits in its walls to-permit it to change its shape when under heat stress and thus conform to the cylinder walls andthereby prevent excessive Wear, tofree lubrication of the wearing surfaces, and above all to provide a path for the dispersion of heatfrom the piston head to the cylinder walls. Still another object is to furnish a piston the outer surface of whose head is co-ncaved or at least provided with a depression or cup for the lodgement of bulks of liquid fuel that are sometimes drawn into the cylinder during starting-operations, to be there held until'consumed instead of being permitted to pass down between the piston and cylinder walls washing away the lubricant therebetween and to enter the crank case to thin the oil therein.

Pistons as most commonly constructed are made up entirely of one type of metal, cast iron for example, which is of low heat conductivity which carries away the heat but slowly, a metal of a very high heat conductivity which, while it conducts away the heat rapidly,-absorbs it just as rapidly from the heat of explosions. My invention contemplates, as differing from both of these, the employment of a head for the piston that will absorb the heat but slowly and then to rapidly carry away and disperse the heat so absorbed by the use of a metal of a different type whereby Others again, are'made wholly'of 1923. "serial No. 640,572.

the engine parts may be-maintained cooler -'within limits, in order that the lubricating properties of the oil shall not be destroyed, and finally that the piston may be of the largest possible diameter in a given bore without undergoing undue wear.

In order that these objects may be attained I construct the body of the piston of a suitable alloy, aluminum alloy being preferable by reason of its light weight and on account of its high heat conductivity.

' The head of the piston is preferably of a metal of low heat conductivity as stated, this being found in such as cast iron which is in thorough contact with the body and secured thereto. Thereby the slowly absorbed heat can be quickly conducted to the walls of the cylinder and taken up in the cooling system. But this will be better understood in the specification "following, aided by the appended drawing wherein:

' Figure 1 is a longitudinal sectional elevation of my improved piston;

Figure 2 is a side elevation of the piston rotated one quarter turn from the position shown in Figure 1. 1

Figure 3 is a transverse section of the piston taken on line 33, Figure 1.

Figure 4 is a transverse section of the piston on line 4-4, Figure 2, and

Figure 5 is a plan of a portion of the pis ton and its head.

The numeral 1 designates the body of the piston as a whole, the skirt thereof being denoted at 2. The body or barrel is an open tube-terminating at its upper end in an inwardly extending flange 3, the usual ringgrooves being indicated at 4 creating landings for the rings not shown. The said upper end and flange 3 receive the pistonhead 5 which is a separate part of cast iron secured to the flange in any suitable manner, in this instance a series of rivets 6 which extend through both the head and the said flange as shown which latter structure admits of replacing the piston head, if and when desired, by another.

' Thesaid head 5 for a piston designed to Preferably the. head is no thicker than dema-nded by the pressure likely to be imposed upon it and is also of a out the same gauge throughout so' as to be as light as possible.

Extending inwardly from the inner walls of the body are bored bosses 8 for receiving the usual piston-pin, not shown, for taking the customary connecting-rod, not shown.

A rib 9 is cast with each boss at its under side and with the wall of the skirt. Likewise a pair of divergent ribs 10 form parts of the body and the top portion of each boss as best shown in Figure 2.

At one side the skirt has a slit extending longitudinally thereof as indicated at 11, said slit extending from the lower edge, through which it opens, up to near the zone of ring-grooves 4 where it communicates with a laterally extending slit 12 extending substantially a sixth of the distance around the skirt but the extent of said slot is merely arbitrary, its purpose being made known v later herein. The lateral slit 12 is repeated at the opposite side of the piston where it is denoted in the drawing by the character 13, there being no longitudinal slit at that side however to correspond with the slit 11. In addition to said slit 11 a pair of slits is provided at opposite sides of the piston. These are denoted at 14 and those of each pair lie at opposite sides of the piston-pin bosses 8 asshown in Figures 2 and 3. Preferably they extend from points substantially in line with the centers of the bosses down to positions substantially midway of the distance between the lowermost ring-groove 4 and the lower terminus of the skirt, though theextent of said slits is merely such as may be found to yield certain desired results now to be described.

I The piston is machined with suflicient clearance according to the variations in thickness of its walls to cause it to maintain a symmetrical outside surface throughout its 'Yength when working at normal heat, the

thickness of metal enclosed between the pairs of slits being reduced somewhat in order that the greater expansion at those places due to the bulk of metal of the bosses 8 and their ribs will not cause/the piston to bind on the cylinder walls and score them. For

somewhat the same reason. the slit 11 provides that the skirt may adjust itself to heat conditions without scoring.

The lateral slit 12 with which the slit 11 communicates may be suflicient in extent to permit the required flexing of the skirt to meet the conditions described. Said slit 12, in addition, and the mentioned slit 13, permit oil. thrown up into the piston to pass through them upon the cylinder walls to aid in lubrication which is also true as to the slits 11 and 14 but to a lesser extent. The main purpose of the slits 14, however,

is that of heat conductance. The heat more or less slowly taken up by the piston-head 5 1s quickly conducted away by the much higher conductivity of the body and skirt, the greatthe zone of metal lying between them is, so

to speak. isolated from the other portions of the skirt sufficiently to cause the heat to travel down said zone in a divided path upon those portions of the piston that lie below said bosses. So-called piston-slap results in those portions of a piston-skirt that lie at opposite ends of a line drawn diametrically through the piston perpendicular to the axis of the piston-pin caused by greater expansion at the zones of the skirt having-said piston-pin with a resulting drawing inward of the portions mentioned. In my piston the zone lying between the slits 14 and which is that prone to greatest expansion in the ordinary piston conducts away the heat so rapidly that the tendency to assume an out-ofround or ellipticah form due to unequal expansion is avoided to a greater or less extent with a resulting lack of the undesirable slap, with a necessarily better operating engine. Stated in another way, the zones lying between the slits 14 guide the heat downward toward the lower end of the skirt where it is dissipated at all points-during piston travel. going across the oil film to the cylinder-wals and taken up by the cooling water. The heat dissipation is so complete that in the lowermost position of the piston the amount of heat remaining is very small and all the heat is carried to those portions of the cylinder that lie at the side of the motor block where heat removal is fastest. Since the portions of metal between the slits are readily relieved of the heat that is retained in older types of pistons it is clear that there must be less expansion of the piston and a less tendency to its distortion.

The reduction in the amount of metal in the boss-zones, as a common expedient, together with the isolated heat conducting paths of those zones jointly contribute in providing the named advantages. Where a piston is composed entirely of one type of metal, for example a metal a low heat conductivity, or one of a high heat conductivity, we have in both cases an engine laboring under heat conditions that are extremely detrimental, there is under lubrication, and greater wear takes place. together with other attendant evils. But by providing a piston of dissimilar metals as described the working parts can be kept within proper heat limits.

It is to be noted that the slits 14 preferably terminate substantia'ly opposite the center of the piston bosses leaving an area of metal uboicihem belowtthe lowermost ring groove 4, the zones of metal outside the pair of slits l-t serving to' better convey away the heat from the head than though said slits terminated close up to the line.

A feature of importance is the cupped piston-head 5 which catches the raw liquid fuel more often drawn into the cylinder in cold Weather. The piston retains thereon such fuel until consumed instead of being permitted to wash down the walls of the piston and cylinder, reducing lubrication and destroying the viscosity of the oil in the crank case.

In order to provide a more intimate union of the piston-head 5 and the body 1 it is preferable to provide some means whereby the Contacting surfacesof these parts are increased in area. For example, I provide a series of concentric grooves 1 in the body 1, Figure 5, while the head 5, Figure 1, has concentric flanges 5 adapted to exactly fit therein and contact at every point. This aids in the ready conductivity of the heat as is clear.

I claim:

1. A piston for an internal combustion engine including a head of a metal of a low heat conductivity, a barrel or body and its skirt of a metal of high heat conductivity, those portions of the skirt having the pistonpin bosses beingseparated into zones extending substantially parallel to the axis of the piston by a slit lying at each side of the bosses cutting through the walls of the said skirt and terminating in spaced relation to that part of the piston carrying the piston rings, the said zones conducting away the heat from said bosses in a direct path toward the open end of the piston substantially parallel to the axis of the latter, there being a circumferentially disposed slot severing the walls of the piston immediately below gines, in combination, a

the piston ring zone and at diametrically opposite sides of said piston abovethe' portion lying between the zones having said bosses, said slots terminating-in a spaced relation to the slits creating the last named zones. c

y 2. In apiston for internal combustion en- 7 piston head of a metal having a lowheat conductivity, and a barrel portion or skirt having a. relatively higher heat conductivity attached thereto, said skirt having at each side of its .pistonpin bosses a slit partially severing its wall and. arranged substantially parallel to the longest axis of the piston, the same extending in the direction of the free end of the skirt" terminating below in spaced relatlon thereto, and terminating above substantially. at points opposite the said bosses an spaced from the piston-ring .zone of said piston, there being a circumferentially d15- posed slot cutting through the walls of the upper portion of each of those parts of the piston lyingbetween the zones having the bosses, each slot lying in spaced relation to each of the slitscreating the said zone and both lying below the said piston ring zone.

3. A piston for an internal combustion engine including a head of a metal of low heat conductivity,-a barrel or body and its skirt of a metal of high heat conductivity, those portions of the skirt having the piston-pin bosses being separated into zones extending substantially parallel to the axis of the piston by a slit lying at each side of each of the bosses cutting through the walls of the said' skirt, the same terminating in spaced relation to that portion of the piston having the piston rings and extending into that portion of the skirt below the bosses, the said zones conducting away the heat from said bosses in a direct path toward the'open end of the piston, the surface of the metal of the created zones being sunken below the periphery of the balance of the piston, there being a circumferentially disposed slot severing the walls of the piston immediately below the piston ring zone and at diametrically opposite sides of said piston above the portion lying between the zones having said bosses, said slots terminating in a spaced relation to the slits creating the last named zones.

4. A piston for internal combustion engines including its piston-pin bosses, there being a slit extending longitudinally of the piston at each side of each of the bosses, each pair of slits creating a zone for conductance of heat from the boss therein toward the open end of the piston, each said boss having a heat conducting rib above and-below it, one of themconducting heat to the boss and the other conducting the heat away from the same.

5. A piston for internal combustion engines including its piston-pin bosses, there being a slit extending longitudinally of the piston' at each side of each of the bosses,

each pair of slits creating a zone for the conductance of heat from the boss thereof toward the open end of the piston, each said boss having a pairof ribs integral therewith diverging toward the head of the piston for conducting heat to the boss, and also having any integral rib for conducting heat away from the boss to said zone.

" 6. A piston for internal combustion engines including in its construction a head 'of a metal of low heat conductivity, and a barrel or body and its skirt of a metal of high heat conductivity including ring-grooves, the wall of the skirt having a slit extending longitudinally thereof from its open end to near the lowermost ring-groove, and a latd erally extending slit at each of two diametrically opposite positions on'the skirt, one of them communicating with the said longi tudinal slit.

7 In a piston for internal combustion engines, in combination, apiston head of a metal having a low heat conductivity, and a barrel portion or skirt having a relatively higher heat conductivity attached thereto, said skirt below the Zone thereof having the usual piston ring grooves being provided with two separate and independent circumferentially arranged slits severing its Wall at two substantially opposite positions, each disposed in one of the zones lying between the positions of the zone having the pistonpin-bosses, the terminals of the slits lying above a circumferential line crossing said bosses, the skirt being otherwise an integral part of said zone for the ring grooves, for conducting heat therefrom, there being a longitudinally extending slit connecting with and extending from one of the named slits extending towardand cutting through the free end of the skirt.

8. In a piston for internal combustion engines, in combination, a piston head of a metal having a relatively low heat conductivity, and a barrel portion or skirt of a relatively higher heat conductivity intimately connected thereto, including a zone for its piston ring grooves, said skirt having a longitudinally arranged slit at each side of each of the piston pin bosses the centers of the bosses and one terminal of each of the several slits lying substantially in line with one another, the other terminals of the slits extending toward the lower end of the skirt and creating a separate zone for each boss separate from the body of the skirt, said skirt also having a circumferentially arranged slit between the said bosses terminating wholly above the line of the same partially separating a portion of the skirt from the said piston rin roove zone whereby the heat conducted from the piston head through the latter will be diverted latterally into those portions of the skirt having said bosses. The terminals of the two sets of slits being separated from one another by intervening metal.

9. A piston for an internal combustion engine including a skirt portion, ring grooves and piston-pin bosses, said skirt having a slit at each side of each of said bosses and extending longitudinally of said skirt, one terminal of all the slits being spaced from the zone of the said ring grooves and lying substantially opposite the center of the said bosses, said skirt also having a circumferentially arranged slit at two diametricallv opposite sides each in the zone lying between the bosses, said slits lying wholly above a circumferential line extending through the said bosses and being spaced from and independent of the first named slits.

10. A piston for an internal combustion engine including a skirt portion, ring grooves and piston-pin bosses, said skirt having a slit at each side of each of said bosses and extending longitudinally of said skirt, one terminal of all the slits being spaced from the zone of the said ring grooves and lying substantially opposite the center ofi the bosses, said skirt also having a circumferentially arranged slit at two diametrically opposite sides each in the zone lying between the bosses, said slits lying wholly above a circumferential line extending throu h the said bosses and being spaced from an independent of the first named slits, there also being a longitudinally extending slit opening through the lower end of the skirt and extending into one of the said circumferentially arranged slits.

11. A piston for internal combustion engines including its body and a separate head-portion of a dissimilar metal, each of the described elements having a plurality of concentric grooves and raised concentric.

flanges in their face surfaces, said elements adapted to be clamped upon one another, and means to clamp said elements together meshing the flanges with said grooves.

12. A piston for an internal combustion engine including in its construction a piston head of a relatively low heat conductivity, and a skirt portion of a relatively higher heat conductivity, and a series of closely arranged rivets extending through the head and part of the said skirt portion securing the two in intimate inseparable relation.

13. A piston for an internal combustion engine including in its construction a skirt portion of a metal of a high heat conductiv-' ity having a series of alternately disposed concentric grooves and flanges at 1ts upper side, and a piston head of a metal of a relatively lower heat conductivity whose lower surface has a series of grooves and flanges complementary to those of the said skirt, the flanges and grooves of both portions being machined to fit in intimate contact, and means to clamp the skirt and head together.

14. A piston for an internal combustion engine including in its construction a skirt portion of a metal of a high heat conductivity having a series of alternately disposed concentric grooves and flanges at one end, and a piston head of a metal of a relatively lower heat conductivity, one of whose surfaces has a series of grooves and flanges complementary to those of the said skirt, the flanges and grooves of both portions being machined to fit in intimate contact, and means to clamp the skirt and head to one another seating the flanges in the grooves.

In testimony whereof I aflix my signature DURWARD EARLE WILLIS. 

